A variety of ideas and devices have been worked out for imparting a stretching property (elasticity) to a textile woven from a spun yarn. For example, a textile which is produced from a composite yarn made of a spun yarn in combination with a polyurethane elastic yarn has a stretching property, and is excellent in a fitting (or clinging) property to the human body as well as a following property to the human motion. Such a textile is comfortable to wear and does not restrict the human motion (or movement) Accordingly, the textile is widely used in clothing applications such as sportswear, underwear (or inner wear) and foundation garments. Moreover, by making use of the stretching property, such a textile is also used in medical applications such as an elastic band age, an industrial material (application) such as a vehicle interior material or a cloth for a belt conveyor, and others.
Typical examples of the composite yarn made of the spun yarn in combination with the polyurethane elastic yarn may include (1) a core spun yarn in which a polyurethane elastic core yarn covered with stable fiber is twisted; (2) a single or double covered yarn in which a single- or double-layered spun yarn is entwined around a core yarn made of a polyurethane elastic yarn; (3) a ply yarn (plied yarn) in which not less than two spun yarns and a polyurethane elastic yarn are twisted together; and others.
Among these composite yarns, the core spun yarn (1) has the same feel as a single spun yarn because the polyurethane elastic yarn is completely covered with the staple fiber. However, in the spinning step of the staple fiber, highly advanced technologies are required to cover the polyurethane elastic yarn with the staple fiber completely, as well as in the knotting by an air splicer used in the spinning step. Therefore, the core spun yarn (1) is difficult to manufacture. In addition, since a large amount of the staple fiber is used in order to cover the polyurethane elastic yarn completely, a finally obtained core spun yarn tends to be thickened. Therefore, it is extremely difficult to produce a core spun yarn of a fine count. Further, it is necessary to sort a raw stock to be used as the staple fiber, and in addition, highly advanced technology is required as described above. Accordingly, the core spun yarn (1) is practically inadequate for small lot productions. Furthermore, although cotton is mainly used as the staple fiber for making a core spun yarn at present, a stable industrial technology has not been established for producing a core spun yarn by using a fiber other than the cotton (for example, other natural fiber such as a hemp or a silk, and a synthetic fiber) as the staple fiber. Additionally, since the core spun yarn is produced by twisting a polyurethane elastic yarn entwined with unspun staple fiber, the yarn strength or stretching property of the core spun yarn itself is not very high. Therefore, the tension or stretching property of a textile made of the core spun yarn is also insufficient. Moreover, since such a core spun yarn is liable to cause fluff on a surface thereof, it is essential to subject the core yarn to a sizing treatment in a process for knitting or weaving the yarn, and in addition, the productivity of the textile tends to be decreased in the knitting or weaving process.
In the covered yarn (2), since a filiform spun yarn is wound around the polyurethane elastic yarn, the covered yarn (2) has excellent yarn strength and good external appearance or touch. Further, a yarn having a desired count ranging from a low count to a fine count is producible. However, since it is necessary to wind the spun yarn around the polyurethane elastic yarn until the polyurethane elastic yarn is completely covered with the spun yarn, the productivity of the covered yarn (2) is low. In addition, the weight of a textile obtained from the covered yarn tends to be increased.
The ply yarn (3) is usually produced by twisting a plurality of spun yarns and a polyurethane elastic yarn after drawing (bundling and drawing) these yarns in parallel to one another (doubling). Therefore, sorting of the raw stock, which is required for the core spun yarn (1) is unnecessary. Accordingly, the ply yarn (3) has a high productivity, and is also applicable to the manufacture of a wide variety of products in small quantities. However, some problems with the manufacturing thereof are prone to occur. For example, the polyurethane elastic yarn can protrude outside two or more spun yarns due to incomplete inclusion of the polyurethane elastic yarn between the spun yarns, or the polyurethane elastic yarn can be cut in the production process of the ply yarn. Furthermore, since two or more spun yarns are used, the production of a fine count ply yarn requires an expensive fine count spun yarn having a yarn fineness of not more than a half of that of an objective ply yarn. Therefore, the production of the ply yarn (particularly, a fine count ply yarn) is not only difficult but also economically disadvantageous.
Japanese Patent Application Laid-Open No. 131838/2001 (JP-2001-131838A, Patent Document 1) discloses a composite twisted yarn in which a single spun yarn and at least one continuous fiber(s) are twisted, wherein the twist direction of the composite twisted yarn and that of the spun yarn is the same, and the twist number of the composite twisted yarn is larger than that of the spun yarn. However, even in the composite yarn, the torque of the twist yarn cannot be reduced, and in addition, the yarn has insufficient yarn strength or stretching property, and feel.
On the other hand, a method for improving a stretching property of a textile made of a spun yarn without a polyurethane elastic yarn is also under investigation. Due to a high stretching property of the polyurethane elastic yarn, a special apparatus and technique are required for handling, or knitting or weaving a composite yarn comprising the polyurethane elastic yarn. Moreover, since the polyurethane elastic yarn is liable to generate degradation with time passage due to heat, light, etc., a composite yarn comprising the polyurethane elastic yarn as well as a textile comprising the polyurethane elastic yarn gradually lose their stretching property. Further, a textile made of a composite yarn containing the polyurethane elastic yarn easily deteriorates in flexibility, soft feel, lightness in weight, and others.
Then, for example, Japanese Patent Application Laid-Open No. 241269/1999 (JP-11-241269A, Patent Document 2) discloses a process for producing a stretchy wool fabric, which comprises providing a fabric made of a mixing (blending) spun yarn comprising a wool fiber and a water-soluble polyvinyl alcohol fiber; soaking (immersing) the fabric in a water bath and raising a temperature of the water bath from an ambient temperature so as to contract the water-soluble polyvinyl alcohol fiber; dissolving and removing the water-soluble polyvinyl alcohol fiber to produce a fabric comprising only the wool fiber; and set-treating the fabric. In this process, however, the mixing spun yarn is low in yarn strength, and in the case of weaving or knitting the yarn with a high-speed weaving machine or knitting machine, difficulties such as thread breakage easily occur. Further, thus obtained wool fabric also has low mechanical properties such as a stretching property or strength. Furthermore, in this process, it is difficult to obtain a stretchy fabric in the case of using a fiber (such as cotton or a synthetic fiber) other than sheep wool.
Moreover, EP Patent No. 1061162B1 (Patent Document 3) discloses a process for manufacturing a fabric made of 100% pure cashmere, which comprises preparing a composite yarn by mixing (or blending) a cashmere yarn with a second yarn that is dissolvable in a slightly acidic aqueous solution at a high temperature; weaving or knitting the obtained composite yarn to make a textile; and dissolving the second yarn in acid to remove it from the textile. However, the fabric of pure cashmere obtained by this process also has an insufficient stretching property. In addition, due to removal of the second yarn with an acid, the residual yarn tends to be deteriorated or have other problems.
[Patent Document 1] JP-2001-131838A (Claim 1, Paragraph No. [0027])
[Patent Document 2] JP-11-241269A (Claim 1)
[Patent Document 3] EP Patent No. 1061162B1 (Claim 1)